SH7760 Datasheet, PDF (849/1345 Pages) Renesas Technology Corp – SuperHTM RISC engine

22.5.8 Transmit Cancel Registers 1 and 0 (CANTXCR1, CANTXCR0)
The CANTXCR are two 16-bit read/conditionally-write registers. The CANTXCR1 controls
Mailbox 31 to Mailbox 16, and the CANTXCR0 controls Mailbox 15 to Mailbox 1. These
registers are used by the microprocessor to request the pending transmission requests in the
CANTXPR to be cancelled. To clear the corresponding bit in CANTXPR, the host CPU must
write a 1 to the corresponding CANTXCR bit. Writing a 0 has no effect.
When an abort has succeeded, the CAN controller clears the corresponding CANTXPR and
CANTXCR bits, and sets the corresponding CANABACK bit. However, once a Mailbox has
started transmission, the transmission cannot be canceled by this bit. In such case, if the
transmission is finishes in success, the CAN controller clears the corresponding CANTXPR and
CANTXCR bits, and sets the corresponding CANTXACK bit, however, if the transmission fails
due to a bus arbitration loss or an error on the bus, the CAN controller clears the corresponding
CANTXPR and CANTXCR bits, and sets the corresponding CANABACK bit. If an attempt is
made by the host CPU to clear Mailbox transmission that is not transmit-pending, it shall have no
effect, and will be automatically cleared when an internal arbitration for transmission runs.
• CANTXCR1
Bit: 15 14 13 12 11 10 9
8
7
6
5
4
3
2
1
0
TXCR1 TXCR1 TXCR1 TXCR1 TXCR1 TXCR1 TXCR1 TXCR1 TXCR1 TXCR1 TXCR1 TXCR1 TXCR1 TXCR1 TXCR1 TXCR1
_15 _14 _13 _12 _11 _10
_9
_8
_7
_6
_5
_4
_3
_2
_1
_0
Initial value: 0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
R/W: R/W* R/W* R/W* R/W* R/W* R/W* R/W* R/W* R/W* R/W* R/W* R/W* R/W* R/W* R/W* R/W*
Bit
Bit Name
Initial Value R/W Description
15 to 0 TXCR1[15:0] All 0
R/W*
Requests the corresponding Mailbox that is in
the queue for transmission, to cancel its
transmission. Bits 15 to 0 correspond to
Mailboxes 31 to 16 (and TXPR1[15:0])
respectively.
0: Transmit message cancellation idle state in
corresponding mailbox.
Clearing condition: Completion of transmit
message cancellation (automatically cleared)
1: Transmission cancellation request made
for the corresponding Mailbox.
Note: * A write of 1 only is allowed for the Mailbox designated for transmission when it is in the
wait state.
Rev. 1.0, 02/03, page 799 of 1294